Method and apparatus for controlling power in wireless power transfer system

1. A method for controlling wireless power transmission, comprising:

transmitting wireless power from a wireless power transmitter to a plurality of peripheral devices within a power transmission coverage of the wireless power transmitter;

receiving, by a power control apparatus, a plurality of control error values from the plurality of peripheral devices;

gradually decreasing an amount of transmission power of the wireless power transmitter until a power reception efficiency of a first peripheral device of the plurality of peripheral devices is reduced below a threshold value;

selecting, by the power control apparatus, the first peripheral device to be a reference peripheral device; and

adjusting, by the power control apparatus, the wireless power transmitted to the plurality of peripheral devices by an amount based, at least in part, on the amount of transmission power when the power reception efficiency of the first peripheral device is reduced below the threshold value and one or more control error values from the reference peripheral device.

2. The method of claim 1 , wherein the adjusting the wireless power provided to the plurality of peripheral devices comprises adjusting the wireless power according to the formula:

t

d

(

j

)

=

t

a

(

j

-

1

)

.

[

1

+

c

(

j

)

1

⁢

2

⁢

8

]

where:

c (j) is a control error value for a j th control error packet,

t a (j−1) is a previous output current for a primary coil of the wireless transmitter, and

t d (j) is an adjusted output current for the primary coil.

3. The method of claim 1 , wherein the power control apparatus operates in a first mode and a second mode, wherein the plurality of peripheral devices comprises a first plurality of peripheral devices, and wherein:

the first mode comprises:

the selecting, by the power control apparatus, the first peripheral device to be the reference peripheral device, and

the adjusting, by the power control apparatus, the wireless power transmitted to the plurality of peripheral devices by an amount based, at least in part, on the one or more control error values from the reference peripheral device; and

the second mode comprises:

receiving power control information from a second plurality of peripheral devices in a time division manner based on a time interval allocated to each of the second plurality of peripheral devices, and

controlling the wireless power in the time division manner based on the power control information of each of the second plurality of peripheral devices.

4. The method of claim 3 , wherein the power control information includes, for each of the second plurality of peripheral devices, at least one parameter selected from a group consisting of a control error value, a rectifier output voltage, and a battery or operating circuit input terminal voltage.

5. The method of claim 3 , wherein the power control information includes, for each peripheral device of the second plurality of peripheral devices, a control error value, rectifier output voltage, or battery or operating circuit input terminal voltage.

6. The method of claim 3 , wherein the power control information includes information about an amount of received power of each peripheral device of the second plurality of peripheral devices and instant consumption power of each peripheral device of the second plurality of peripheral devices.

7. The method of claim 3 , wherein the power control information includes a ratio of an actual amount of received power to instant consumption power for each of the second plurality of peripheral devices.

8. The method of claim 3 , wherein the power control information includes a current charging level for each of the second plurality of peripheral devices.

9. The method of claim 3 further comprising:

determining actual power consumption states of the second plurality of peripheral devices based on the power control information from the second plurality of peripheral devices; and

wherein controlling the wireless power is based on a comparison of the respective power consumption states of each of the second plurality of peripheral devices.

10. The method of claim 1 , wherein the adjusting the wireless power of the wireless power transmitter includes causing the wireless power to be transmitted by a resonant circuit of the wireless power transmitter to the plurality of peripheral devices within the power transmission coverage of the wireless power transmitter.

11. The method of claim 1 , wherein the wireless power transmitter is configured to transmit the wireless power to the plurality of peripheral devices via electromagnetic induction or via a resonant frequency signal.

12. The method of claim 1 , wherein a control error value of the plurality of control error values comprises a value determined based, at least in part, on an amount of power received by a peripheral device compared to an actual amount of power consumed by the peripheral device.

13. The method of claim 1 , wherein a control error value of the plurality of control error values comprises a value determined based, at least in part, on an amount of power measured at an input terminal of a rectifier.

14. A wireless power transmission system, comprising:

a wireless power transmitter configured to transmit wireless power to a plurality of peripheral devices within a power transmission coverage of the wireless power transmitter;

a communication unit comprising one or more first processors configured to receive a plurality of control error values from the plurality of peripheral devices; and

a control unit comprising one or more second processors configured to operate in a first mode to:

gradually decrease an amount of transmission power of the wireless power transmitter until a power reception efficiency of a first peripheral device of the plurality of peripheral devices is reduced below a threshold value,

select the first peripheral device to be a reference peripheral device, and

adjust the wireless power transmitted by the wireless power transmitter, based at least in part, on the amount of transmission power when the power reception efficiency of the first peripheral device is reduced below the threshold value and one or more control error values received from the reference peripheral device and transmit the wireless power to the peripheral devices.

15. The wireless power transmission system of claim 14 ,

wherein the control unit is configured to operate in a second mode,

wherein the plurality of peripheral devices comprises a first plurality of peripheral devices, and

wherein in the second mode, the control unit is configured to:

receive power control information from a second plurality of peripheral devices in a time division manner based on a time interval allocated to each of the second plurality of peripheral devices, and

control the wireless power in the time division manner based on the power control information of each of the second plurality of peripheral devices.

16. The wireless power transmission system of claim 15 , wherein the power control information includes information about an amount of received power and instant consumption power for each of the plurality of peripheral devices.

17. The wireless power transmission system of claim 15 , wherein the power control information includes a ratio of an amount of received power to instant consumption power for each of the plurality of peripheral devices.

18. The wireless power transmission system of claim 15 , wherein the power control information includes a current charging level received from each of the plurality of peripheral devices.

19. The wireless power transmission system of claim 14 , wherein the control unit is configured to adjust the wireless power according to the formula:

t

d

(

j

)

=

t

a

(

j

-

1

)

.

[

1

+

c

(

j

)

1

⁢

2

⁢

8

]

where:

c (j) is a control error value for a j th control error packet,

t a (j−1) is a previous output current for a primary coil of the wireless transmitter, and

t d (j) is an adjusted output current for the primary coil.